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Flexural Deformity - Donkey (view source)
Revision as of 23:24, 19 February 2010
, 23:24, 19 February 2010no edit summary
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[[Image:Working donkeys.jpg|right|thumb|150px|<small><center>Working donkeys (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
=Distal interphalangeal joint flexural deformity=
[[Image:Flexural deformity donkey.jpg|right|thumb|250px|<small><center>Flexural deformity (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
[[Image:Stage 2 flexural deformity donkey.jpg|right|thumb|250px|<small><center>Lateral radiograph of stage 2 contracture showing hoof wall past vertical and demineralisation of tip of pedal bone. (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
Flexural deformity of the distal interphalangeal joint is seen in donkeys. In the UK it is usually recognised in young rapidly growing animals on a relatively high plane of nutrition and may have the same multifactorial aetiologies as in the horse. Working donkeys overseas also suffer the condition – often in such a severe form that the dorsal hoof wall becomes parallel to the ground surface. In these cases, overwork, concurrent distal limb pain and nutritional deprivation may play a role.
==Clinical signs==
As in the horse, the deformity may be referred to as:
*'''Stage 1''', where the dorsal hoof wall has not passed the vertical
*'''Stage 2''', where the dorsal hoof wall has passed the vertical
==Diagnosis==
Donkey foals and young stock should have their hoof-pastern-axis (HPA) regularly assessed on a firm surface.
==Treatment==
Those that are starting to show flexural deformity should have the '''plane of nutrition reduced''' and conservative treatment measures instituted. These measures include '''rasping the heels''' to restore a normal HPA and possible application of '''corrective glue shoes''' to protect the toes from excessive wear.
In cases where a '''Stage 2 deformity''' is present, '''surgery is required''' to correct the defect.
==Surgery==
[[Image:Lateral view pre-tenotomy donkey.jpg|left|thumb|200px|<small><center>Lateral view pre-tenotomy (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
[[Image:Lateral view post-tenotomy donkey.jpg|right|thumb|200px|<small><center>Lateral view post DDF tenotomy mid-cannon, also using ‘glue-on’ therapeutic shoe. (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
[[Image:Shoe with toe extension.jpg|right|thumb|200px|<small><center>Shoe with toe extension (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
[[Image:Post-tenotomy radiograph donkey.jpg|right|thumb|200px|<small><center>Post-surgery radiograph showing shoe (Image courtesy of [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary])</center></small>]]
Pre-operatively, '''radiographs''' should be taken to assess the distal phalanx; degenerative changes reduce the likelihood of a good outcome. The degree of tension and any abnormal thickening or pain in the flexor tendons should be assessed. At [http://drupal.thedonkeysanctuary.org.uk The Donkey Sanctuary] we like to arrange for a skilled farrier to be present during the assessment and subsequent surgery. This enables the farrier to be able to apply glue-on shoes while the donkey is still slightly sedated. If more than one limb is to be operated on, front limbs can be operated on with a two-week delay between surgeries, or a fore limb and contra-lateral hind limb may be
operated on simultaneously, with a two-week gap for the opposing limbs.
There are three sites for performing the surgery, the simplest being '''tenotomy of the deep digital flexor tendon (DDFT) in the mid-cannon'''. This can be performed in the standing animal under [[Sedatives and Tranquilisers|sedation]] and [[Local Anaesthetics|local anaesthetic]]. This operation results in a pasture-sound animal, and even working donkeys have performed acceptably after the surgery. There is, however, thickening and scarring in the mid-cannon area.
DDFT tenotomy can also be performed in the '''mid–pastern'''. In this site the tendon sheath is penetrated and the operation must be carried out under '''general anaesthetic'''.
A better cosmetic result is obtained, but problems can occur if the cut tendon recoils within the sheath.
'''Desmotomy of the accessory ligament of the DDFT''' is the third method of surgical treatment. again this requires '''general anaesthesia'''. This technique is only really suitable for Stage 1 deformities. In the donkey an extra head on the accessory ligament may reduce the effectiveness of this surgery (N. Matthews, personal communication).
===Tenotomy of the DDFT in the mid-cannon site===
This can be performed in the '''standing, sedated donkey'''. For analgesia a '''subcarpal nerve block''' is used and/or '''local skin infiltration'''. The leg is clipped and prepared aseptically. A small '''skin incision''' is made on the '''lateral''' aspect
of the limb at the '''mid-metacarpal level'''. The tendons are identified manually and curved artery forceps used to '''separate the DDFT''' from the superficial digital flexor tendon (SDFT). Care must be taken to <u>avoid the blood vessels and nerves coursing laterally</u>. A tenotome is inserted into the DDFT and turned through 90º so that the '''DDFT is divided'''. At this
point a significant gap should appear and the tendon can be checked for complete severance. The '''subcutis and skin is sutured routinely''' and the '''leg bandaged'''. [[NSAIDs#Phenylbutazone|Phenylbutazone]] is administered post-op for five to seven days.
After this procedure, the farrier can apply a shoe with a toe extension to help in realigning the HPA. Although theoretically over-extension of the hoof could occur, in practice we have not experienced this.
The donkey should have '''box rest for 10 to 14 days''', then '''restricted exercise''', depending on its temperament. If they are not restricted, young boisterous animals can over-exercise and delay healing of the tendon, while sensible animals may heal adequately on paddock rest.
==References==
* Thiemann, A. (2008) Surgery In Svendsen, E.D., Duncan, J. and Hadrill, D. (2008) ''The Professional Handbook of the Donkey'', 4th edition, Whittet Books, Chapter 16
For more details on this condition in the donkey, the following references are suggested:
* Carmona, A.G., Sevilla, M.A.T., Sevilla, H.C., and Cabanas, A.L. (1997). ‘Correccion de la contraccion del tendon flexor profundo por medio de un herraje ortopedico en equidos’. ''Vet.Mex.'' 28 (2). pp175-177.
* Daniels, L.E., Conine, T.A., and Jackson, D.A. (1990). ‘A rehabilitation team approach to correct flexural deformities in a donkey foal’. ''Canadian Veterinary Journal 31''. pp 297-299.
* Walmsley, J.P. (1995). ‘Flexural deformities of distal interphalangeal joints in a group of young donkeys’. ''Equine Veterinary Education 7''(1). pp 4-6.